Anyone happen to know the porosity (pores per square inch or MERV #) of the foam air filter for a 360, 363 or 390 (i suspect there all the same)? I can't find specs for the air filter (that must be oiled) anywhere.
I would like to think that tests have been conducted to maximize airflow yet filter a certain size particle out. Lycoming only gives a spec of no more the 6" water pressure drop across the filter. No particle size restriction. The Lycoming technical support rep was surprised that the most recent suggestion dates back to 1963.